1. Field of the Invention
The present invention generally relates to a digital broadcast receiving device and a method thereof, and more particularly, it relates to a digital broadcast receiving device capable of efficiently providing viewers with information about programs transmitted from a broadcasting station, and a method thereof.
2. Description of the Prior Art
Since the US DirecTV enforced digital satellite broadcasting in 1994, the digital broadcasting has been enforced or prepared globally. The rival media, cable television, is digitalized in Europe and the USA thereafter and all broadcasting media is being digitalized since the terrestrial broadcasting which gained attention launched its trial broadcast in USA and UK in November 1998. Korea also opened an era of digital broadcast with a trial of digital satellite broadcasting in July 1996 and the Korean Broadcasting System (KBS) successfully broadcasted the national first digital terrestrial broadcasting in May 1999, ranking Korea among the advanced countries in the field of digital broadcasting.
The characteristics of digital broadcasting can be summarized by three features, namely, a multi-channel, high quality, and a multi-function. Among the above features, the multi-function means that, besides image and sound, a variety of additional services can be provided using data channels, and that is the most significant characteristic which can differentiate the digital broadcast from the analogue broadcast.
Due to the advancement of the multiplex technology, the digital broadcasting can transmit image, sound, and data simultaneously in a bundle regardless of the content and size. In addition, since the digital broadcasting is provided with the return channel through a modem, interactive service is possible, and a processor and an operation system inside a receiver make various receiving functions possible. Owing to the advancement of such technologies, the digital broadcasting became able to provide one step upgraded multimedia service to viewers beyond additional service realized in the existing analogue broadcasting.
In the digital broadcasting system capable of realizing a variety of service as above, a broadcasting signal includes largely program data and Program and System Information Protocol (PSIP) data.
The program data is TV programs provided by a broadcasting station for being broadcast to subscribers and includes user information such as video data, audio data, and caption data. The program is provided in a Transport Stream (TS). The TS is an agreement which video, audio and data are simultaneously transmitted in a single stream in the Motion Picture coding Experts Group (MPEG)-2 system. The TS is comprised of one or more programs, and TS header includes information about programs constituting the whole stream, program time information, and control information for controlling overall system. The TS packet is comprised of 188 bytes and has 4-byte header in the upper portion. The sync byte is one byte, and cannot be used in other parts that are periodically repeated, for example, Packet Identifier (PID). The PID, which is comprised of 13 bits, is an ID for identifying packets. The TS packet is comprised of pure data such as video, audio and data and the Program Specific Information (PSI).
The PSI information is data repeatedly transmitted in a fixed time period for initialization in a receiver and is comprised of table structure divided by sections of 1024 bytes. The PSI information begins with Table_id. In addition, the PSI information includes Program Association Table (PAT) information, Program Map Table (PMT) information, Condition Access Table (CAT), and private section. Among the PSI information, the PAT information is the table having “0” PID. The PAT information functions to inform the PMT PID. The PMT information informs the content of streams included in a program and the PID. The CAT information provides information for limited reception. The private section is a section that can be used by a user by choice and the PSIP information uses this section.
The Program and System Information Protocol (PSIP) data is a group of tables designed to be included inside the TS for digital television. The purpose of the PSIP information is to disclose information of a virtual channel for specific TS. The PSIP information hierarchically combines factors describing particular service of a digital television at respective channels. Such PSIP information includes a modulation method of each channel required for normal reception of each channel broadcasting program, carrier frequency, packet ID information for inverse-multiplexing video and audio information from the packet stream transmitted via a carrier channel, program information (i.e., program title, commencing time, synopsis) whether caption service is provided or not, program classification, and current time.
Accordingly, when a digital broadcast channel is selected, the digital broadcast receiver is synchronized to the selected broadcast channel, separates PSIP data from the packet stream and stores the separated PSIP data in the internal memory, and inverse-multiplexes video and audio data by using the stored PSIP data. The PSIP data include base table data including system time table (STT) data, rating region table (RRT) data, master guide table (MGT) data, and virtual channel table (VCT) data, and data containing PID data defined in the MGT such as event information table (EIT) data and extended text table (ETT) data. PID data is a special ID provided to discriminate among multiple elementary stream (ES) in the TS. PID data is positioned in the TS header.
STT data is one of PSIP data in advanced television system committee (ATSC) standard, which provides information about current date and time. RRT data is one of PSIP data in ATSC standard, which provides level information of plural regions. MGT data provides PID data which correspond to version numbers of all the PSIP data except STT data operating independently of the other tables, table length, and table type. VCT data describe information about virtual channel, and include therein information such as major channel number, minor channel number, modulation mode, carrier frequency, program number, ETM location data indicating the location of the PSIP data where detailed information about virtual channel and event exists, and service type.
EIT data contain information about program content. EIT data also contain event information (title, starting time) about the virtual channel defined by the PSIP data. One piece of EIT data contain event information lasting about three (3) hours, and total 128 pieces of EIT data can be transmitted by from EIT-0 to EIT-127. ETT data refer an option table used in describing in the PSIP data the virtual channel and event in greater detail.
The digital broadcast receiver receives PSIP data and PSI data provided by the broadcasting station. However, as some information such as ETT data contained in the PSIP data carry considerable amount of text data about current broadcast, viewers usually do not understand the currently-broadcasting program and ETT data immediately.